Correcting Git Author for Multiple Commits using git-filter-branch

Problem

$ git log
commit 9feb12e957a554214c5dc7ed4543546676f59580
Author: Too <too1@babygrace.llnl.gov>
Date:   Thu Dec 22 17:30:08 2016 -0800

    Add drafts

I have been writing on this blog using a new laptop (babygrace.llnl.gov) with a different username (too1). As you can tell in the above commit message, the author line reads:

Author: Too <too1@babygrace.llnl.gov>

A couple problems with this information:

1. Too is not my name. This should read Justin Too
2. too1@babygrace.llnl.gov is not my Github email address. This should read justin@doubleotoo.com

Since I’ve made many commits with this incorrect information, I’ll have to update multiple commits, which are interspersed with other peoples’ commits - kind of a tricky situation.

Solution

One time fix using git-filter-branch

Using git-filter-branch, I can go through every commit in the history and change the commit author where it is wrong:

# change-author.sh
git filter-branch --env-filter 'if [ "$GIT_AUTHOR_EMAIL" = "too1@babygrace.llnl.gov" ]; then
     GIT_AUTHOR_EMAIL=justin@doubleotoo.com;
     GIT_AUTHOR_NAME="Justin Too";
     GIT_COMMITTER_EMAIL=$GIT_AUTHOR_EMAIL;
     GIT_COMMITTER_NAME="$GIT_AUTHOR_NAME"; fi' -- --all

The if conditional checks each commit for the incorrect email address too1@babygrace.llnl.gov. Where detected, I update the Git author information using the relevant Git environment variables (GIT_AUTHOR_EMAIL, GIT_AUTHOR_NAME, GIT_COMMITTER_EMAIL, GIT_COMMITTER_NAME).

For ease of use and convenience, I added the git-filter-branch command into a script file, titled change-author.sh and then ran it with bash:

$ bash change-author.sh
Rewrite 9feb12e957a554214c5dc7ed4543546676f59580 (1031/1417)

Permanent fix using git-config

Of course, I want future commits to be using the correct author information too so before making my next commit, I updated the global Git configuration to reflect this:

$ git config --global user.name "Justin Too"
$ git config --global user.email

Environment

Item	Description
Operating System	OS X El Capitan version 10.11.6
Git	git version 2.6.4 (Apple Git-63)
Bash	GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin15)